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Advice on first quadcopter: Will this fly? (researched)

Posted by BossEd on October 24, 2013 at 3:39pm

Hi everyone,

For the people not interested in reading my entire story but who are inclined to answer a few quick questions, these are the questions the story will end with (based on the wishlist down below):

  • Is the engine / propeller / 4cell battery choice a good one to lift ~2100 grams?
  • Is there a better solution i overlooked? (3 cell with 12 inch propellers maybe?)
  • Is there any reason to assume this will not fly at least 10 minutes with a 5000mah battery? (I've checked http://ecalc.ch but since I'm not sure how to enter the engines data into it i cannot get a decent calculation)

Now onto some prose!

Last week i got the chance to play around a bit with a DJI Phantom, and since that I've been researching hours and hours if it's feasible to built my own. Flying it is great but the real challenge for me seems to be the introduction to working / building with electronics. As a side note, i am a software engineer from profession and have been scared to enter the domain of electronics. However this has kept my interest for a full week now so i think it's actually time to get crackin'.

I've set myself a few goals, which are as follows:

  • i'm going to build a quadcopter assembled and built by myself (no complete package)
  • I'm aiming high, 
  • i want the finished product to be able to do FPV video
  • (gimball assisted) GoPro footage (all this in due time with small increments)
  • GPS enabled for safe return after radio failing
  • Access to the code, being able to make tweaks / enhancements if i want to later on.


I know all these are feasible given the correct build and budget.

On these I also have to be realistic and have a few expectations:

  • this is not going to be the lightest quad, therefore it's not going to be the fastest thing in town. That's fine, the goal is to get cool FPV and video.
  • Due to the weight i'm expecting poor fly time, but have trouble actually figuring out what a realistic number is. 10 minutes at least is the goal, but more would be great


The goals /demands for the first phase are then as follows:

  • expandable
  • flies
  • is capable of flying with GOPRO mounted (should be able to lift this weight)
  • should be able to carry ~2100grams (later phases will add more weight, FPV, GOPRO)
  • flight time at least 10 minutes

After research I've made a few conclusions (which maybe wrong, because to be honest.. the physics of the motors and the propellers is still a bit hazy to me)


  • I want to use a battery in 4s configuration, the extra voltage gives me more power to lift the entire quad / setup
  • I want to use bigger propellers then standard due to the weight and this also seems to provide a more stable flying copter.

As i said before the mathematics of the brushless motors elude me a bit (the combinations of RPM/V / propellorsize / battery cell count, but i have to start
somewhere. This resulted in the following wishlist:

The frame was an easy choice.. i want it light.. and according tot he specification it can lift way more then i'm putting on there.. so fine. Looks nice too ;)

APM 2.5 seems to fit my requirements as (wasn't confident that the hobbyking copy is just as reliable)

The receiver / transmitter is 8 channels because i want the possibility to expand to functions like gimball operation or GPS home function.. 2.4ghz has better range
then 5 ghz, and anything else is illegal or has possibility of jamming. Also "cheap enough" to replace one day and for phase meets my requirements


Now comes the wiggly part.. my first choice was the 4 cell 5000mah battery. The extra voltage give me extra capability to lift my ~2100 grams (final setup). I'm also pretty sure i can safely hook up a 3 cell battery which i can borrow from a friend to see if it still flies well enough but with longer flight time.


The motor id a bit of a gamble, and i would love some feedback on this. Too low RPM means too big a propeller and amperage, but higher RPMs seem to be for acrobatic light quads. The 800kv seemed to be somewhat on the lower KV side of the middle, which would translate well to the 11 inch propellers (one set clockwise, one set counterclockwise).


For the ESC i chose the 30amp HobbyKing, because well.. it's rated better then i need and this has a 5v BEC (my other option a Turnigy ESC had 5.5volt). The Arduino Pilot seems to like 5v and not 5.5v.

So, wow.. what an epic text ;) Let's finish off with the questions i started with!

  • Is the engine / propeller / 4cell battery choice a good one to lift ~2100 grams?
  • Is there a better solution i overlooked? (3 cell with 12 inch propellers maybe?)
  • Is there any reason to assume this will not fly at least 10 minutes with a 5000mah battery? (I've checked http://ecalc.ch but since I'm not sure how to enter the engines data into it i cannot get a decent calculation)

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Tags: apm 25, battery motor propellor combo, quadcopter
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Replies

  • Jonathan van der Riet August 23, 2015 at 12:10pm

    Please also see this configuration and let me know what you think?

    Thanks in advance

    http://diydrones.com/forum/topics/diy-hexacopter-project

  • matt October 27, 2014 at 11:12am

    one of the best write-ups i have seen. did you flash your esc's i am using a similar setup. plan on putting my go pro on but currently my

    sk450 quad weighs out at about 938grams without battery

    ntm800kv 300 watt motors  downgraded from the 1200kv ntm long shaft

    30 amp hobby king blue series esc's

    kk2.1 board

    range of batteries from 2200 3s to 5000 3s 50 c range

    have used everything from 8-10 inch props

    turnigy 9x controller

         the note about 300 watts draining batteries faster, so would the 150 watts give me twice the hover time?  mostly does that mean that i am just stuck using massive batteries? and not being able to exceed 10 minutes. i have good leveling and control input but i am stuck with pretty shitty flight times.

  • Austin Suhler October 26, 2013 at 9:46pm

    Wow, seriously impressed with the amount of research you have done. I recommend starting with an SK-450 frame for that setup, then moving to the talon. I have 2 SK-450's, one on a KK2.0 board, and one on an APM 2.5+, and they are really cheap and almost indestructible frames. Can only really do 10-11 inch props though with the size, but try flying without any gimbal or even a camera, and learn the ropes. Multirotors fly like nothing else out there, as I have learned over the last year, and as I've reiterated many times to my now flight students, two of which are struggling after 8 years of RC plane and heli experience. Start simple, and only go more advanced as your skill increases. This way your repairs will be cheap, the complexity of our machine matches your flying capabilities all the time, and your wallet will have some time to get those payments out, not just one lump sum :) Oh yeah, did I mention the replacement parts? You will need those..... a lot ;)

    Just a note though, I do have those exact motors on the SK 450s. They seem to be happy on 3s, but 4s was a little more iffy. I think this was just because I had the wrong size props though, so get a range of them and test them out. On my 1.03kg quad with 1 2650mha 3S batteries, I get 8-10 minutes of rock solid flight, and that includes my running LED lights on the arms for orientation. I imagine you will get better flight times on 4s. Also, if you do get the talon frame, let us know what you think of it! I've been thinking of it as my next upgrade.

    • Robert Howard > Austin Suhler March 22, 2014 at 1:33am

      Austin,

      I Have the same motors listed above on a Hobby King X650 frame (550MM wheelbase) using the KK2.1 with Steveis 1.14 firmware.

      I am currently running 10" props (most stable) but have had a tough time getting the P and I gains set so that the system is stable using larger props.  I have gone up to 13" props with very questionable results.  My fear is that the motors, props, or something is preventing a stable hover.

      V = 11.1

      20A ESC

      Thanks for your help in advance.

      Robert 

  • Barre Wheatley October 26, 2013 at 9:30pm

    I am a newbie also having only flown a Parrot Drone which really is more or less a toy but a good introduction to quads. I can only speak from what I have experienced putting together the Arducopter quad kit. Although it is a kit I definitely learned a lot about how things work and why. The nice part is I felt very confident that it would work. What amazed me is the complexity of the quad. Setting up the Mission Planner was a learning experience in itself. I am not trying to discourage you from purchasing pieces and part and doing your own thing. I am just speaking to your comment about wanting to learn how it works and why. I learned a heck of a lot with the kit and if I had to do it all over again I would do the same thing. With my new knowledge I am considering a scratch build like you at some point in the future. I personally like scratch building. I think going the kit route saved me a lot of money and frustration in the long run. It has given me a good knowledge of quads, compasses, GPS, video, telemetry etc..... We are having a ball flying the drone and taking it one step at a time. I wish you good luck no matter what you do but don't shy away from a kit. I think you will be surprised how much you learn and there is a lot of support help to get you going.

  • BossEd October 25, 2013 at 9:42am

    Hi guys,

    Thanks for the detailed replies!

    Getting a complete kit to me kind of feels like cheating, i want to know WHY it flies (or not) and experiment with it, i want to feel that i actually understand it.. making mistakes is part of the learning. Also the need to maybe solder a bit to get things fitted and such is part of the fun. Buying a complete kit takes away from the fun of knowing and building in my opinion.

    It's not my intention to mount fpv or gopro on the second, or third flight ;). That would be a second or third phase of the project. I will be enjoying a few hours of flight time and tinkering before going to that phase.

    Multiple batteries and buying redundant sets are on my list, first time I've flown a quadcopter was for only 10 minutes.. and that time really does fly... if you'l pardon the pun ;)

    The weight I mentioned of 2100grams is the total estimated weight of the quadcopter by the way, including frame, motors, gopro and gimball setup. The motors need to be able to lift it whenever i will feel comfortable going to the next phase of adding it, not coming to the conclusions the motor / prop combo is too weak to lift and fly it properly.

    That being said i will ponder a bit about the complete kit, but i'm still feeling very strongly about the talon frame.

    What engines can you recommend in combination with 12 inch props? - It seems that not each same KV rated motor is the same, they have different power usages / amp usages. I would imagine that same KV but higher AMP / WATT means more power.

  • mP1 October 24, 2013 at 8:31pm

    Like Gary said, small steps. Try one thing at a time. Dont try and do FPV on your second flight. Get aquainted with each of the flight modes one at a time. Dont assume stuff will just work, there are lots of parameters and each one may or may not affect the performance of something. Dont think you wont crash, because you will. The APM only does what it is told and theres no point crashing with all the fancy extras attached to it.

    I would seriously consider buying spares. Props are cheap so dont buy just 4, buy 10 or 20. You will eventually need them. You might also need some spare arms and legs, because you will crash and you will break one or two. I would also recommend buying at the least 4 batteries. You will be surprised how little time you get from 4 batteries, 40 minutes sounds like a lot, but when you need to check things and possibly adjust things on a computer it quickly runs out.

  • Gary McCray October 24, 2013 at 4:17pm

    Hi BossEd,

    Like many people new to this "hobby" you are trying to do everything you could think of the first time out, I started that way too, 5 quadcopters ago.

    When you are starting, light and indestructible are the most important considerations and after you have thoroughly exercised those 2 features then you can start thinking about endurance and utility - for your second or third copter.

    First please carefully read this wiki page that I wrote: http://copter.ardupilot.com/wiki/build-your-own-multicopter/

    What you have basically outlined will probably work although 2 kilos is certainly more weight than you want to start with.

    The heavier it is the harder (and more destructively) it lands / falls / crashes and you are kidding yourself if you think you aren't going to be spending a fair amount of time doing that.

    I would actually recommend that you start with one of the genuine DJI F450 Flamewheel kits as the motors, frame and ESCs are all excellent and known quality and work very well together. And the frame and all the parts are really rugged and can handle imperfect landings very well. http://www.amainhobbies.com/product_info.php/cPath/2_382_2405_3233_...

    That said, the Talon frame, Turnigy motors and ESCs you have spec'd will probably work although I would consider going with something with a lower KV motor 450-650 so you can turn the props a bit slower and use bigger 12 to 14" props on the Talon frame.

    Basically all things being equal, larger props = considerably greater overall efficiency and longer hover time.

    But the motors have to be rated above hover current at that RPM or they will overheat and burn out.

    The DJI F450 comes stock with 10" props and Gemfan has a DJI motor compatible carbon filled prop that is inexpensive and very rugged. It can take 11 or 12" props but the prop hubs will require reaming to fit the DJI motor hubs. You can run 3 or 4 cell on an ARF 450, but you should not run larger than 10" props using 4 cell.

    With a 4000 mah LiPo, the F450 will easily let you exceed 10 minutes flying time and can reasonably support a brushless gimbal and GoPro camera or an FPV setup or both.

    If you want to use a bigger camera or a heavier payload, wait until your second copter to try that.

    And infact you should get in at least a couple hours of straight flying without a camera, gimbal or FPV system before you even add the parts to your copter to give yourself plenty of time to familiarize yourself with it flying light.

    They are also a lot more fun and responsive to fly with as little unnecessary weight as possible.

    I would also recommend that you get a Pixhawk for only slightly more money than the APM as it is going to be the flight controller of choice from now an and the APM will soon be retired.

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